This invention relates to embedding a printed circuit in a recessed surface of a molded plastic article. More specifically, the invention relates to embedding a printed circuit in adjoining non-coplanar recessed surfaces of a molded plastic article wherein the printed circuit is continuous from one adjoining surface to the other.
It is well known to deposit a printed circuit on an insulating substrate by photographic, screen printing or similar methods. The conductive portions of printed circuits formed by these methods are raised above the surface of the substrate. In some printed circuit applications, the raised conductive elements are not suitable and methods are known for forming inlaid printed circuits wherein the face of the circuit elements are flush with a surface of an insulating base usually plastic. Inlaid printed circuits are preferable in switching and commutating applications wherein it is desired to protect the conductors from erosion or cracking during repeated operations. The printed circuit is customarily formed on a flat substrate which is then mounted within the switching or commutating apparatus in which it is to be used. Subassemblies of this type generally add to the overall cost of the apparatus.
This invention is directed to providing a printed circuit directly on a molded plastic article of the electrical apparatus such as directly on the housing for such apparatus. Known photographic methods for depositing a printed circuit directly on the housing member are unsatisfactory when the location of the printed circuit is to be at the bottom of a recessed portion of the molded plastic article primarily because it is difficult to remove photoresist material from interior corners and sharp crevices. Screen printing requires a flat surface and is not suitable for use in recessed areas.